P0031-O2 SENSOR 1/1 HEATER CIRCUIT LOW





For a complete wiring diagram Refer to Section 8W.


  • When Monitored:

    Battery voltage above 10.6 volts, ASD is powered up, and O2 heater is powered.

  • Set Condition:

    Desired state does not match Actual state. One Trip Fault. Three good trips to turn off the MIL.


Possible Causes
 
(K99) O2 SENSOR 1/1 HEATER CONTROL CIRCUIT SHORTED TO GROUND
 
O2 SENSOR
 
PCM
 


Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).



Diagnostic Test

1.O2 SENSOR HEATER OPERATION


NOTE: Wait a minimum of 8 minutes to allow the O2 Sensor to cool down before continuing the test. Allow the O2 Sensor voltage to stabilize at 5.0 volts.






Does the O2 Sensor voltage stay above 4.5 volts?

Yes
  • Go To 2


No

2.O2 HEATER ELEMENT


NOTE: Allow the O2 Sensor to cool down to room temperature.




NOTE: O2 Heater Element resistance values should be measured at 21.1° C (70° F). The resistance value will vary with different temperature values.



Is the O2 Sensor Heater Element resistance between 2.0 and 30.0 ohms?

Yes
  • Go To 3


No

3.O2 SENSOR





NOTE: Make sure the test light is probing the circuit before actuating the Heater Test or a DTC may set and not allow the actuation.




Does the test light illuminate brightly and flash on and off during the actuation?

Yes


No
  • Go To 4

4.(K99) O2 1/1 HEATER CONTROL CIRCUIT SHORTED TO GROUND







Is the resistance below 5.0 ohms?

Yes


No
  • Go To 5

5.PCM

NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.




Were there any problems found?

Yes


No